章节大纲

  • 常规

    全部折叠 展开全部

  • 生命周期

    What will you learn
    ::你会学到什么

    • Haploid and diploid life cycles
      ::嗜血类和低脂生命周期
    • The alternation of generations life cycle
      ::几代人生命周期的交替

    Silhouettes of young people jumping joyfully beside an older man with a cane at sunset.

    Young to old. A life cycle?
    ::年轻到老 生命周期?

    Not in the biological sense. Life cycles describe the amount of present at a specific stage or time in the life of an organism . Is there a haploid or diploid amount of DNA? That is the key question.
    ::不是生物意义上的。 生命周期描述在生物体生命的特定阶段或时间的当前数量。 是否有零散或低位的DNA? 这是关键问题 。

    Life Cycles
    ::生命周期

    occurs in a cycle. Diploid parents produce haploid gametes that unite and develop into diploid adults, which repeat the cycle. This series of life stages and events that a sexually reproducing organism goes through is called its life cycle . Sexually reproducing organisms can have different types of life cycles. These are described in the following sections.
    ::在循环周期中发生。 Diplioble 父母生产混合的偶发调子,它们会结合并发展成重复周期的潮湿成人。性再生生物经历的一系列生命阶段和事件被称为其生命周期。性再生生物可以有不同类型的生命周期。下文各节对此作了说明。

    Haploid Life Cycle
    ::嗜血类人寿命周期

    The haploid life cycle is the simplest life cycle ( Figure ). It is found in many single-celled eukaryotic organisms. Organisms with a haploid life cycle spend the majority of their lives as haploid gametes. When the haploid gametes fuse, they form a diploid zygote . It quickly undergoes to produce more haploid gametes that repeat the life cycle.
    ::偶然的生命周期是最简单的生命周期( 图表 ) 。 它在许多单细胞电子气理生物中都能找到。 周期性生物在周期性生物中的大部分时间都以杂交游戏形式度过。 当杂交游戏引信发生时, 它们会形成一个极低的zygote。 它会很快发生,以产生重复生命周期的更多杂交游戏。

    The haploid life cycle, showing gametes, zygote, and meiosis stages.
    The haploid life cycle.

    Diploid Life Cycle
    ::代数寿命周期

    Organisms with a diploid life cycle ( Figure )spend the majority of their lives as diploid adults. When they are ready to reproduce, they undergo meiosis and produce haploid gametes. Gametes then unite in and form a diploid zygote, which immediately enters G 1 of the . Next, the zygote's DNA is replicated. Finally, the processes of and cytokinesis produce two genetically identical diploid . Through repeated rounds of growth and division, this organism becomes a diploid adult and the cycle continues. Can you think of an organism with a diploid life cycle? ( Hint: What type of life cycle do humans have?)
    ::生物的生命周期( 图表) 覆盖了他们大部分的寿命。 当他们准备繁殖时, 他们会经历美化, 并生产杂交的游戏。 调子随后聚集并形成一个didloid zygote, 立即进入 G1 。 下一步, zygote的DNA被复制。 最后, zygote 的过程和细胞基尼西斯 产生两个基因相同的低潮。 通过反复的生长和分裂, 这个生物会变成一个低潮的成年人, 周期还会继续。 你能想到一个具有低潮生命周期的有机体吗 ? (Hint: 人类有什么样的生命周期? )

    The diploid life cycle, showing stages from gametes to grown individual.
    The diploid life cycle.

    Alternation of Generations
    ::代代相传

    Plants, , and some have a life cycle that alternates between diploid and haploid phases, known as alternation of generations ( Figure ). In plants, the life cycle alternates between the diploid sporophyte and haploid gametophyte . Spore-forming cells in the diploid sporophyte undergo meiosis to produce spores , a haploid reproductive cell. Spores can develop into an adult without fusing with another cell. The spores give rise to a multicellular haploid gametophyte , which produces gametes by mitosis. The gametes fuse, producing a diploid zygote, which grows into the diploid sporophyte. These life cycles may be quite complicated. You can read about them in additional concepts.
    ::植物、 植物和某些植物的生命周期可以交替在低潮期和低潮期之间, 被称为代际交替( 图表 ) 。 在植物中, 低潮植物和低潮植物之间的生命周期交替。 低潮植物中的微粒成形细胞会经历 meicisation, 以产生螺旋, 一种杂交生殖细胞。 微粒可以发展成成人, 而不与其它细胞发生交融。 螺旋可以产生一种多细胞的低潮植物。 螺旋会通过线状体产生调子。 调子的导体, 产生低潮和低潮植物。 这些生命周期可能非常复杂。 您可以从其他概念中读到它们。

    The life cycle alternation of generation in plants between sporophytes and gametophytes.
    The alternation of generations.
    DID YOU KNOW?
    The jellyfish life cycle involves the alternation of generations between stationary, asexually reproducing polyps and mobile, sexually reproducing medusae .
     

    Summary
    ::摘要

    • A life cycle is the sequence of stages an organism goes through from one generation to the next.
      ::生命周期是生物体一代又一代经历的各个阶段的顺序。
    • Organisms that reproduce sexually can have different types of life cycles, such as haploid or diploid life cycles.
      ::性繁殖的生物可以有不同种类的生命周期,如杂交或低潮的生命周期。

    Review
    ::回顾

    1. What is a life cycle?
      ::什么是生命周期?
    2. An adult organism produces gametes that quickly go through fertilization and form diploid zygotes. The zygotes mature into adults, which live for many years. Eventually, the adults produce gametes, and the cycle repeats. What type of life cycle does this organism have? Explain your answer.
      ::成年有机体会生成快速通过受精和形成低脂酶的调子。 zygotes会成熟成成年人, 他们活了多年。 最终, 成人会生成调子, 循环会重复。 这个有机体的生命周期是什么样的? 请解释一下答案 。
    3. Which life cycle is the simplest? Why?
      ::哪个生命周期最简单?
    4. Describe the life cycle with alternation of generations.
      ::用世代的交替来描述生命周期。